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CHAPTER 10 – BLOOD 1. Blood is the ONLY fluid tissue. It is red in color and made up of living blood cells that are suspended in a nonliving fluid matrix called the plasma. It looks homogenous, but if spun in a centrifuge the living cells separate out from the plasma. 2. Plasma makes up 55% of the blood content. Plasma is 90% water and has over 100 different substances dissolved in it. Examples: nutrients, metal ions (salts), O2 & CO2, hormones, plasma proteins and various wastes. Plasma proteins are the most abundant, except for antibodies and protein-based hormones, most plasma proteins are made in the liver. Albumin helps maintain osmotic pressure in the blood. If blood proteins drop too low, the liver is stimulated to make more proteins. If blood becomes too acidic, or too basic, the respiratory system and kidneys help restore the 7.35 – 7.45 pH. 3. Erythrocytes main job is to transport oxygen to all cells. They are anucleated (lack a nucleus) and contain few organelles. They are filled with an iron containing protein called hemoglobin. The RBCs produce ATP for themselves anaerobically, therefore not using oxygen. Their small size and biconcave (depressed center) shape provide a large surface area relative to volume, making them well suited for gas exchange. On average, there are about 5 million cells/mm3. The more hemoglobin in the blood, the more O2 it can carry. One RBC contains about 250 million hemoglobin molecules, each one can bind with 4 O2 molecules, which means each RBC can carry 1 billion oxygen molecules. Normal blood contains 12-18 grams of hemoglobin per 100ml of blood. (Men have slightly higher levels 13 – 18g, women 12-16g). Disorders – anemia, sickle-cell anemia, polycythemia. RBCs are formed by hemocytoblast stem cells originally, then the myeloid stem cell. 4.WBCs, also called leukocytes, are less numerous than RBCs (4,000 – 11,000/mm3.) They contain nuclei and organelles, are formed by the same stem cell as RBCs. WBCs are involved with the immune system which defends the body against “foreign” invaders. WBCs can move into and out of the blood vessels and respond to certain chemicals that are produced by damaged cells. When the WBCs are battling invaders the body produces more. A total WBC count of 11,000 cells/mm (leukocytosis) is common when your body is fighting a virus or bacterium. Leukopenia is abnormally low WBC count, caused by certain drugs such as anticancer agents. There are two major groups of Leukocytes. Granulocytes – have a granular cytoplasm 1. Neutrophils- active phagocytes, increase during short-term infections. 2. Eosinophils – kill parasitic worms, increase during allergy attacks. 3. Basophils – contain histamine (inflammatory chemical) which is discharged at the inflammation site. Agranulocytes – lack visible cytoplasmic granules 1. Lymphocytes – part of the immune system. B cells produce antibodies, T cells fight tumors and viruses & activate B cells. 2. Monocytes – largest WBCs, active phagocytes which become macrophages in the tissues. They are important in fighting chronic infections such as tuberculosis. 5. Platelets are fragments of multinucleate cells called megakarocytes which rupture leaving thousands of pieces. They are needed for clotting blood. (300,000/mm3) 6. Hematopoiesis – blood cell formation, occurs in the red bone marrow (myeloid tissue). In adults, this tissue is found in flat bones of the skull, pelvis, ribs & sternum and the proximal epiphysis of humerus and femur. Each type of blood cell is produced in different numbers in response to changing body needs and different stimuli. After they mature, they are discharged into the blood vessels surround the area. Hemocytoblast – common stem cell that forms the blood cells. Hemocytobalsts form two type of descendants, the lymphoid stem cell which produces lymphocytes and the myeloid stem cell which produce the other parts of the blood. Hemostasis – stopping blood flow